Spark-plug tool



c. A. scHu-Lz 2,235,172

SPARK-PLUG TOOL Original Filed Feb. 17, 1938 'WAMA INVENTOR ATTORNEY Patented Mar. 18, 1941 Q S A Q T Q 1; v y a Christopher A. Schulz, Gutten berg, NLJJaSSignor" I corporation of New York Original application February Serial 190,953; now Patent No. 2,193,886, dated March 19,1940; Divided and this application January h [2.1940, seria n qs aosz f I 2Clainis. (Crista-48) face, usually in the form of wide prongs, the" inner sides of which have a curvaturesimilar to" that of the center electrode surface so that the inner surfaces of the prongs are uniformly spaced from the center electrode surface.

The spark jumps between the center electrode and the prong electrodes, sometimes from one part of a surface, sometimes from another, with the result that wear on the electrodes is greatly reduced. When any parts of the electrodesu'rfaces become pitted or-worn, the spark dischargesbetween other points that remain at the correct spacing. In order to obtain-the long'ser vice for which spark plugs of this kind are suitable under 'ably with a forming die for shaping the prong electrodes and with a bending device for effecting afinal adjustment of the spark gap between the electrodes. J I V -This application is a division of my copending application Serial No. 190,953, filed February 17,

1938 (Patent No. 2,193,886, dated March 19,

1940). i 1 r r Other objects, features and-advantages of the invention will yappear'or be pointed-"out-asj the speclficationproceeds.

In the accompanying drawing, forminga part hereof: T I

Fig. 1 is a front elevation of a tool embodying this invention and shown with the plunger against a spark-plug shell for forming the electrode surface of the shell.

Fig. 2 is a sectional view taken on the line 22 of Fig. 1.

Fig. 3 is a reduced perspective view of the tool, showing the manner in which the tool is used to adjust the spacing of the electrode surfaces of the spark-plug.

Fig. 4 is an enlarged sectional view through the carriage, gauge, and adjusting foot of Fig. 3,, the parts being. .shown the same r'elation'as in Fig; 3.f I Fig. 5"i's' a sectional vi'ew on'the line 5 5 of The. embodiment pf'the invention shown in the drawing has, a. frame I'D with'countersunk screw holes" l 'lthrou'gh itsbase foranchoring' tionfor the tool isldesired.

A. circulaf'ba'r' has gearjt'eeth'cut in one side to form" .a'frack. This'bar will ,be referred'to hereinafter" as'fthe' rack bar 1 3.. There is a vertical bearingjld' inthe frame l0, and the'rack the frame 'to' a work benchif apermanent lo'cabariislides up and down-in that bearing." A

horizontal. shaft Ilfturnsj in bearings in the frame l'llr'a'ndhas gear teeth cut init to form a pinion l8 that engages the rack I3. "'Theshaft l 'l is turned by a .handrwheel 1.9 that is rigidly secured to one end ofthe shaft.

The 'hub of the halid.-wheel 19 contacts with aj boss rithe'sideof the frame in, and the shaft 11 isjustlong enough to extend through its hear ing in; the frame. [A washer 20 is' held-against the'end of the" shaft l'l'by alscrew-fl that threads into the, end of the shaftlf The-washer 20 contactswit'h a boss on the side of the frame to prevent" displacement of the shaft l'l tothe right,'in Fig. 1, and the hub of the hand-wheel I9 pr'events displacement of the shaft ;I1 toward the left. For thef use of deft-handed operators, however, the-screw Zl'and washer ZQca'n be-removed and tlna'j'shaft llpulled "out of "its bearings and inserted'from the'left side of the frame. j

The-rack 'bar l3- hasfa tapered lower end in whichhi s a fsocketfl23. The bottomof, the rack banisformed into a 'die,='which is indicated generally by the reference-character 25. Thus the bottom end-of therackb'ar is itself a: tool in the illustrated embodiment ;of the invention, but the die can be a separate piece and attached to the lower 'end'of 'the'rack bar; On the base o.f,the frame in thereisa 'carriag'e-guideway including asupporting surface 21 with guide surfaces 28 extending along both the front and back edges of the surface 21.

A die 30, which is shaped for the particular spark-plug sleeve that is to be formed, has a stem 3| that fits into a socket 32 in the base of the .frame and in line with the rack bar l3. A hardened insert 34 in the surface 21 at the upper end of the socket 32 prevents the surface from being scratched or nicked by the die or the shoulder of the die that rests on the insert 34.

A spark-plug shell 36 fits over the die 30, and the upper end of the die is substantially the shape desired for the discharge surface of the shell. The actual dimensions of the die 30 are a little oversize so that the prongs 31 at the end of the shell 36 are spaced a few thousandths too far apart and can be bent into exact position as determined by a thickness gauge.

The rack bar is lowered until the die is in contact with the shell 36. The rack bar is then struck on the top with a hammer once or twice to bend the prongs at the end of the shell to the exact contour of the die. The die 25at the bottom of the rack bar I3 is shaped so that it has a drawing action over the die rather than a true forming action as understood in the die art. The operation is referred to herein as the forming of the shell,-however, using the term in its broader sense.

The die 30 is held in position by a die lock pin 38 clamped against the stem 3| by a set-screw 39 threading through the forward wall of the base. 5

After the forming of the shell 36 in the manner described above, the shell 36 is screwed onto the rest of the plug 4|, as shown in Fig. 4, and the assembled spark-plug is inserted through a bush ing 43 and threaded into a face plate 44 of a carriage 45 until the shoulder 41 of the plug comes against the end of the bushing 43.

The carriage 45 rests on the supporting surface 21 and has a width substantially equal to the distance between the guide surfaces 28, best of movement of the rack bar l3, a set-screw 50,

threaded into the front of the frame III, is tightened against the carriage 45 to lock it in position. I

The carriage 45 includes a body portion 52, a part of which extends upward at a substantial acute angle to the vertical as shown in Fig. 4. The face plate 44 has a sleeve 53 extendin from its back face. This sleeve 53 fits into the upstanding part of the carriage body 52, and is held in the carriage body by a set-screw 54,'tha.t extends. into circumferential groove 55 in the sleeve 53 and leaves the sleeve and the face plate 44 free to rotate.

The bushing 43 surrounds the tops of the outside threads of the shell 36 and limits the extent to which the spark-plug can be screwed into the face plate 44 by providing an abutment against which the shoulder of the spark-plug strikes. The bushing 43 has a circumferential groove registering with a groove on the inside surface of the sleeve 53, and a spring 59 confined in these grooves holds the bushing against displacement from the sleeve. The spring 53 yields, however, to permit the bushing to be forced from the sleeve when a longer bushing is to be inserted for a different model of sparkp g.

An electrode adjusting foot 6| has an enlarged upper end that fits snugly into the socket 23 in the bottom of the rack bar l3. The adjusting foot 6| is held fast in the socket by a set-screw 62 (Figs. 1 and -2) and the rack and pinion mechanism is operated to bring the adjusting foot down against the uppermost prong 31 of thesparkplug shell 36. A thickness gauge is inserted between the center electrode of the spark-plug and the uppermost prong 31 of the shell; the hand-wheel is then operated, and the prong is pressed against the thickness gauge with sufficient force to reduce the clearance between the electrode surfaces to the dimension of the thickness gauge.

The face plate 44 is turned to bring each of the four prongs on the end of the shell 36 successively into position under the adjusting foot 6|. Fig. 3 illustrates the manner in which an operator holds the thickness gauge 64 in one hand and turns the hand-wheel IS with the other hand. The handwheel is of such a size in relation to the size of the pinion and other parts that no injury to the plug will be caused with any reasonable force that is applied to the hand-wheel.

The preferred embodiment of the invention has been illustrated and described, but modifications can be made and some features of the invention may be used without others.

I claim: I

1. A spark-plug adjusting tool includin a member movable up and down in a frame, means supporting a spark-plug with its electrode end control the position of the electrodes with respectv to the plate and said member.

2. A tool for adjusting the spacing'of the electrodes of a spark-plug that has a center electrode surrounded by a plurality of prong electrodes extending from the spark-plug shell,as'aid tool coni- 1 prising a frame in which is a guideway, a rack bar slidable in the frame toward and from the guideway, a carriage-that is movable lengthwise in the guideway and is supported. by and held against transverse movement by bearing surfaces of said guideway, means on the frame operable to hold the carriage against movement lengthwise of the guideway, a holder on the carriage with an opening for receiving a spark-plug and an' abutment for positioning the spark-plug in a definite position in said holder with the axis of the sparkplug extending at an acute angle to the direction of movement of the rack bar, and a bearing on the carriage in which the spark-plug holder is rotatable about an axis substantially coincident with the axis of the plug.

CHRISTOPHER A. SCHULZ. 

